Angiography is a procedure used in the detection and treatment of abnormalities or restrictions in blood vessels. During angiography, a radiographic image of a vascular structure is obtained by injecting radiographic contrast material through a catheter into a vein or artery. Vascular structure fluidically connected with the vein or artery in which the injection occurs is filled with contrast material. X-rays are then passed through the region of the body in which the contrast material was injected, with the x-rays being absorbed by the contrast material, creating a radiographic outline or image of the blood vessel containing the contrast material. The x-ray image of the blood vessels filled with the contrast material is usually recorded onto film or videotape and then displayed on a fluoroscope monitor.
During angiography, after a physician places a catheter into a vein or artery, the angiography catheter is connected to either a manual or automatic contrast injection mechanism. With a typical manual contrast injection mechanism, a syringe and catheter combination are used wherein the user depresses the plunger of the syringe to inject the contrast. Such a method allows the user to feel the resistance to injection so that he or she can adjust pressure accordingly.
Given the relatively small diameter of the catheter and the potentially viscous nature of the contrast, the injection of such material can often be difficult to perform manually. This is especially true when quick injection is required. Consequently, automatic contrast injection mechanisms have been devised. Such mechanisms use a power-actuator to drive the plunger of a syringe. Examples of such automatic machines are disclosed in U.S. Pat. Nos. 5,515,851 and 5,916,165.
However, while a power-actuated plunger is employed with such devices, the user is provided with no indication as to the resistance encountered by the fluid being injected. In both devices, touch pads or buttons are provided which, upon depression, cause the injection of the fluid to be initiated. Removal of pressure from the actuation buttons causes the injection process to be stopped. Not only is the user provided with no feedback as to the resistance encountered by the fluid being injected with such devices, but the control apparatus of such devices is of a foreign nature to most clinicians. Most clinicians are normally used to the operation of a syringe type mechanism, wherein the plunger of the syringe becomes more difficult to depress as output pressure increases.